Memory Card Problems

The memory card for our camera recently housed several hundred pictures.  I spent lots of time uploading them to my computer and also online to Walmart Photo so I can print some.  Since many of the pictures were old, and we needed the space, I deleted the photos so that I had room for some new ones.  Well, after doing this, the memory card proceeded to "fill up" rather quickly. Today, I transfered 10 pictures to my computer, and when the memory card was completely empty, it said that there was no space available!  It is a 1.0 GB memory card for crying out loud!! Does anyone know what I am doing wrong???